GNOP(8) 						    BSD System Manager's Manual 						   GNOP(8)

NAME

     gnop -- control utility for NOP GEOM class

SYNOPSIS

     gnop create [-v] [-e error] [-o offset] [-r rfailprob] [-s size] [-S secsize] [-w wfailprob] dev ...
     gnop configure [-v] [-e error] [-r rfailprob] [-w wfailprob] prov ...
     gnop destroy [-fv] prov ...
     gnop reset [-v] prov ...
     gnop list
     gnop status
     gnop load
     gnop unload

DESCRIPTION

     The gnop utility is used for setting up transparent providers on existing ones.  Its main purpose is testing other GEOM classes, as it allows
     forced provider removal and I/O error simulation with a given probability.  It also gathers the following statistics: number of read
     requests, number of write requests, number of bytes read and number of bytes written.  In addition, it can be used as a good starting point
     for implementing new GEOM classes.

     The first argument to gnop indicates an action to be performed:

     create	Set up a transparent provider on the given devices.  If the operation succeeds, the new provider should appear with name
		/dev/<dev>.nop.  The kernel module geom_nop.ko will be loaded if it is not loaded already.

     configure	Configure existing transparent provider.  At the moment it is only used for changing failure probability.

     destroy	Turn off the given transparent providers.

     reset	Reset statistics for the given transparent providers.

     list	See geom(8).

     status	See geom(8).

     load	See geom(8).

     unload	See geom(8).

     Additional options:

     -e error	   Specifies the error number to return on failure.

     -f 	   Force the removal of the specified provider.

     -o offset	   Where to begin on the original provider.

     -r rfailprob  Specifies read failure probability in percent.

     -s size	   Size of the transparent provider.

     -S secsize    Sector size of the transparent provider.

     -w wfailprob  Specifies write failure probability in percent.

     -v 	   Be more verbose.

SYSCTL VARIABLES

     The following sysctl(8) variables can be used to control the behavior of the NOP GEOM class.  The default value is shown next to each vari-
     able.

     kern.geom.nop.debug: 0
	     Debug level of the NOP GEOM class.  This can be set to a number between 0 and 2 inclusive.  If set to 0, minimal debug information is
	     printed.  If set to 1, basic debug information is logged along with the I/O requests that were returned as errors.  If set to 2, the
	     maximum amount of debug information is printed including all I/O requests.

EXIT STATUS

     Exit status is 0 on success, and 1 if the command fails.

EXAMPLES

     The following example shows how to create a transparent provider for disk /dev/da0 with 50% write failure probability, and how to destroy it.

	   gnop create -v -w 50 da0
	   gnop destroy -v da0.nop

     The traffic statistics for the given transparent providers can be obtained with the list command.	The example below shows the number of
     bytes written with newfs(8):

	   gnop create da0
	   newfs /dev/da0.nop
	   gnop list

SEE ALSO

     geom(4), geom(8)

HISTORY

     The gnop utility appeared in FreeBSD 5.3.

AUTHORS

     Pawel Jakub Dawidek <pjd@FreeBSD.org>

BSD
								  April 14, 2013							       BSD